There is no language to describe Zen. One must achieve his understanding through an enlightenment experience. Since seventeen years old I had been seized with doubt concerning this matter. After I struggled for seventeen years I finally could rest. Before I achieved enlightenment I often thought to myself: I am now already of such and such an age. Before I was born on this earth, where was I? My mind was pitch-black and had no idea where I came from. Since I did not know my origin, this was what Buddhism calls, "Life is a great matter" (sheng ta). When I die in the future, where shall I go? When I thought about this, my mind was also totally dark and had no idea where I would go from here. Since I did not know my destiny, this was what Buddhism called, "Death is a great matter" (ssu ta). 

When you stabilize the activities of the discursive mind and consciousness, when not even one thought stirs, this is the true enlightenment. With this correct state of mind, you can function freely during the twenty-four hours of the day. Smelling flowers, tasting food, sitting still or walking around — whether you are engaged in activity or not, your mind is always bright and undisturbed. You are naturally free from distorted views. Thus your mind is always pure whether you have thought or not. Therefore, when you act, this is the function (yung) of this deep and luminous Mind, and when you rest, this is then the essence (t'i) of the same Mind. Even though there is a difference between essence and function, the Mind is still the one and the same.

No-mind does not mean the unconsciousness of wood or tile. It means that when you come into contact with external objects, your mind is immovable and does not get attached to anything. There is total freedom and non-obstruction. You are not defiled by anything. On the other hand, you should not abide in non-defilement either. While you view the body and the mind as a dream and an illusion, you nevertheless do not abide in the emptiness of dreams and illusions. When you reach this state, you have then really achieved no-mind. 

-Zen Master Ta Hui